/* Yet Another Forum.NET
 * Copyright (C) 2003-2005 Bjørnar Henden
 * Copyright (C) 2006-2013 Jaben Cargman
 * Copyright (C) 2014-2020 Ingo Herbote
 * https://www.yetanotherforum.net/
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at

 * https://www.apache.org/licenses/LICENSE-2.0

 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

namespace YAF.Core
{
    #region Using

    using System;
    using System.IO;
    using System.Text;
    using System.Web;
    using System.Web.Caching;
    using System.Xml;
    using System.Xml.Serialization;

    using YAF.Types.Extensions;

    #endregion

    /// <summary>
    /// The load serialized xml file.
    /// </summary>
    /// <typeparam name="T">
    /// </typeparam>
    public class LoadSerializedXmlFile<T>
        where T : class
    {
        #region Public Methods and Operators

        /// <summary>
        /// The attempt load file.
        /// </summary>
        /// <param name="xmlFileName">
        /// The File Name. 
        /// </param>
        /// <param name="cacheName">
        /// The cache Name. 
        /// </param>
        /// <param name="transformResource">
        /// The transform Resource.
        /// </param>
        /// <returns>
        /// </returns>
        public T FromFile(string xmlFileName, string cacheName, Action<T> transformResource = null)
        {
            if (HttpRuntime.Cache.Get(cacheName) is T file)
            {
                return file;
            }

            if (!xmlFileName.IsSet() || !File.Exists(xmlFileName))
            {
                return null;
            }

            lock (this)
            {
                var serializer = new XmlSerializer(typeof(T));
                var sourceEncoding = GetEncodingForXmlFile(xmlFileName);

                using (var sourceReader = new StreamReader(xmlFileName, sourceEncoding))
                {
                    var resources = (T)serializer.Deserialize(sourceReader);

                    transformResource?.Invoke(resources);

                    if (cacheName.IsSet())
                    {
                        var fileDependency = new CacheDependency(xmlFileName);
                        HttpRuntime.Cache.Add(
                            cacheName,
                            resources,
                            fileDependency,
                            DateTime.UtcNow.AddHours(1.0),
                            TimeSpan.Zero,
                            CacheItemPriority.Default,
                            null);
                    }

                    return resources;
                }
            }

        }

        #endregion

        #region Methods

        /// <summary>
        /// The get encoding for xml file.
        /// </summary>
        /// <param name="xmlFileName">
        /// The xml file name. 
        /// </param>
        /// <returns>
        /// </returns>
        private static Encoding GetEncodingForXmlFile(string xmlFileName)
        {
            var doc = new XmlDocument();

            doc.Load(xmlFileName);

            // The first child of a standard XML document is the XML declaration.
            // The following code assumes and reads the first child as the XmlDeclaration.
            if (doc.FirstChild.NodeType == XmlNodeType.XmlDeclaration)
            {
                // Get the encoding declaration.
                var decl = (XmlDeclaration)doc.FirstChild;
                try
                {
                    var currentEncoding = Encoding.GetEncoding(decl.Encoding);
                    return currentEncoding;
                }
                catch
                {
                    // use default...
                }
            }

            return Encoding.UTF8;
        }

        #endregion
    }
}